Johannesburg — Words like ''remarkable'' and ''amazing'' were commonly used to describe Zimbabwe through its first 20 months of independence. Now analysts say the nation belatedly is showing the social and economic strains that might have been expected when Robert Mugabe won power and colonial rule ended in April 1980.
The latest jolt for Zimbabwe was a huge bomb blast Dec. 18 that devastated Mr. Mugabe's political party headquarters in Salisbury. It has been described as the most serious act of sabotage since the days of guerrilla war. Six people were reportedly killed.
Mugabe quickly dispelled any notion his government was threatened by leaving the country the next day for a previously planned state visit to Mozambique. He declined to point an accusatory finger at South Africa, as had been done earlier by the state-run Zimbabwe Broadcasting Corporation.
Still, analysts see the explosion as further evidence that Zimbabwe is struggling to maintain an even keel. In recent months numerous incidents have been reported of racial friction between whites and blacks.
At the same time the economy has deteriorated and Mugabe's leadership criticized by other black politicians.
''The situation seems to be unraveling a bit,'' says Michael Spicer of the South African Institute of International Affairs.
''That sense of euphoria is wearing off,'' agrees a diplomatic source in Salisbury.
Perhaps the greatest challenge facing Mugabe is to maintain his policy of ''reconciliation'' between the races that he has promoted since taking office. The recent bomb blast - if perceived by blacks as a white effort to destabilize government - will no doubt make reconciliation more difficult.
Mugabe was quoted recently in the South African press as stating in an interview, ''The situation we have is one where the blacks regard whites with suspicion.''
The government itself seems suspicious that whites may be plotting to overthrow the ruling party. Wally Stuttaford, a white member of Parliament, and a member of Ian Smith's Republican Front Party, has been detained by the government reportedly for alleged conspiracy.
Reconciliation is particularly important in Zimbabwe because the nation depends heavily on whites for skilled labor to run its fairly well developed economy.
Still, early predictions that Zimbabwe's white population would eventually whittle down to some 100,000 - from a peak of about 277,000 in 1976 - seems on target. Statistics reported by Zimbabwe the same day as the explosion showed a higher-than-average emigration for October of 1,964. While not differentiated by race, most of those leaving are assumed to be white. The black population of Zimbabwe is just over 7 million.
A shortage of skilled labor is exacerbating other economic problems for Zimbabwe. After years of enjoying an inflation rate lower than most of the outside world, Zimbabwe's consumer prices are rising at a 15 percent annual clip , and are accelerating.
Zimbabwe has been plagued with transportation problems this year. The withdrawal of 26 locomotives by South Africa in April at the end of a lease agreement made it difficult for the country to move goods. There is hope this will be corrected with the delivery of 60 new locomotives from Canada and the United States by the middle of 1982.
Meanwhile, Mugabe has been raising minimum wages; comsumption is shooting upward as a result. The nation's balance of payments situation is worse as imports rise to meet consumer demand.
While analysts say the Zimbabwe economy remains ''fundamentally strong,'' it has deteriorated considerably since 1980. Overall, real economic growth in 1981 is expected to be only half what it was last year.
How Mugabe handles the economy is seen as the barometer of how fast he intends to introduce some of his socialist ideology. Western diplomatic sources have given Mugabe considerable credit since taking office for steering a careful course between pragmatism and ideology.
Yet analysts see continuing strong pressure on the prime minister from both right and left. Former Prime Minister Abel Muzorewa, more moderate than Mr. Mugabe, has made political hay from the country's economic woes.
And from the left, Mugabe is under constant pressure from elements in his own ZANU-PF (Zimbabwe African National Union - Patriotic Front) party to move faster on a socialist path, analysts say.
The way one diplomatic source described it, Zimbabwe was impressive in the transitional phase from colonial rule to independence. But now it is struggling with ''those problems that any developing country must deal with.''